Memorial Boulevard Rigid Frame

Back in July of 2009 I rated a rigid frame in Providence RI which carries Memorial Boulevard over a pedestrian underpass. The frame spans 40 feet allow foot traffic to the Providence and Woonsaquatucket River where each year the Waterfire festival is held. The frame was constructed in 1994 and has several unique features.

The reason I remembered this bridge is from reading tallbridgeguy's post on Green Bridge and Landscaping, where he mentions the positives of adding flower plants and trees along with negatives freeze/thaw (a big problem in New England), drainage, extra load and maintenance.

Along with planters the bridge also has a glass atrium which allows light to the underside of the frame and decorative tiling along the legs of the frame.

These decorative accents help create an aesthetically pleasing bridge which is the goal for both a consultants and a necessity for clients when it comes to pedestrian traffic. When it comes to this bridge tho these accents can cause problems down the road. As most would suspect the glass atrium now has several broken panes, the tiles do not allow for inspection of the legs and the underside of the roof below the plants have cracking with efflorescence, incrustation and stalactites. 

The rating of the concrete rigid frame was performed using influence lines to determine the maximum live load effects and we treated the rigid frame's support conditions as pinned-pinned.

The architectural “waffling” on the underside of the rigid frames was not considered as a structural component and was not taken into account as part of the section properties. 

  

Prestressed Concrete I-Beam Rating

Last February I worked on a rating for MassDOT on two simple span prestressed concrete I-beam bridge with an 8" composite deck. The bridges were built in 1982 and carries route 146 through Sutton MA. The bridges span 78'-4" with a 8°-22'-09" skew.

I used Virtis to perform the rating of the prestressed concrete I-beams.  The rating of the reinforced concrete deck was computed by hand in accordance with the AASHTO Standard Specifications and MassHighway Bridge Manual.

The prestressed concrete I-beams have a set of 16 straight low relaxation strands and 7 harped or draped relaxation strands. At first I had trouble modeling the beams in Virtis and would come up with rating factors lower than 0.05. At first I thought the strand pattern may have been incorrect or a material was entered wrong. After exhausting all the typical mind fart errors, we were able to figure out a problem with the live load modeling.

When we inspected the bridge to confirm measurements and gather other information we noticed that the majority of the prestressed beam ends had areas of rust staining with minor cracking throughout but nothing serious enough to effect the rating.  

ACROW Truss Rating

Back in March I finished a rating for an ACROW temporary truss located in Russell MA. The bridge was constructed in 1986, to allow access to a factory after truck traffic was stopped over a now closed three span arch. The bridge spans over the Westfield River near a large mill and dam.

The three spans consist of two double single reinforced and one double double reinforced trusses.

The rating was our first ACROW rating and was pretty complex, we were able to break the rating down into 6 different parts.

First we checked the deck which consists of several 2.33' x 4.97' panels that weigh 282 pounds.

Next we looked at the transoms (floorbeams) which we treated as a simple span between the two truss members.

After the transoms we looked at the shear at the pinned connections which are located at each truss panel.

We then looked at the shear at the supports looking at the top and bottom cords which consist of eight to twelve channels.

Then we looked at the flexure near midspan using the section modulus of the truss and the dead load and live load moments.

Finally we checked the buckling of the top cord which ended up being the most complex part of the rating.

The bridge is located in a beautiful area which I will have to visit again. 

Stone Masonry Arch Rating

 

Catching up, This August I worked on a MassDOT rating for a stone masonry arch in Uxbridge MA. The arch was built in 1900 and rehabilitated in 1936 and 1960 and spans 39.5 feet over the Blackstone River.

The 1936 rehabilitation consisted of adding a 1’-6” concrete slab in the spillway and pointing the arch ring. The 1960 rehabilitation consisted of adding concrete railings and concrete tie beams.

  

The stone masonry arch is founded on stone masonry abutments with concrete backing.

This was my first time rating a masonry arch but soon after I had to rate an unreinforced concrete masonry arch in Providence RI.

The rating took a few iterations but we were able to derive a complete rating that was well above the statutory loads.

For the inspection we were able to use a 62 foot under bridge inspection unit (UBIU) which was able to reach all parts for the arch.

After figuring out the soil pressure and the dead loads for the spandrel wall and pavement, I input them into STAAD to find the axial and moment coefficients.

Using the coefficients I was able to find the location of for the maximum reactions of the axles and then figure out whether the thrusts were located within the kern.

Wrentham Rating Inspection

Down in Wrentham MA confirming measurements for a rating. Taunton Street over I-495 northbound.

Tough Commute

From Boston.com

This morning it took me two hours to reach my office by far one of my worst commutes to work. With bad weather, bad drivers and bad tires I was extremely happy when I was inside and safe.

Oldies but goodies

In my office on MLK day and will be posting some past bridges that I missed. Since it's MLK day take some time out of your day and check out the Martin Luther King Bridge which is a cantilever steel through truss in Saint Louis, Missouri.